Regular exercise, such as weight lifting, is widely known to increase a person's resistance to certain diseases, e.g., cardiovascular disease, and to generally improve a person's fitness, appearance, and overall physical and mental health. Accordingly, a regular exercise regimen that includes weight lifting is beneficial to many people.
Unfortunately, weight lifting requires the lifting and manipulation of relatively cumbersome and unwieldy free weights, leaving a novice or untrained lifter subject to injury. Not surprisingly, a number of devices have been introduced that make use of weights to improve the muscle tone and cardiovascular fitness, yet which avoid the risk of injury inherent with free weights. Such devices, familiarly referred to as "weight machines", typically include a manipulable mass that is lifted by the user through various mechanisms, such as levers and cable pulley systems. Regardless of the system used, weight machines typically restrict the motion of the mass to a single, vertical direction so that the mass cannot develop hard-to-control inertial motion in a lateral direction as it is being vertically lifted, which is the bane of free weights. Consequently, exercising with weight machines is comparatively safer than exercising with free weights.
Furthermore, the ability to isolate the force vector to a single direction permits weight machines to be designed to help the user focus on developing a preselected muscle--more so than may be possible through the use of free weights. More particularly, through the careful arrangement of levers, cables and pulleys, weight machines can be designed to force the user to exercise a particular muscle group, to the exclusion of other muscle groups. This focusing prevents the user from unintentionally "cheating" by using additional muscle groups to assist in lifting the mass.
To optimize the weight training benefit provided by a weight machine, it is desirable that the moving parts of the machine move smoothly while requiring the application of a substantially constant force to move the mass through its entire range of motion. It is also desirable that the machine be adjustable to accommodate the physiques of different users, both in terms of body strength and size. Moreover, it is desirable that the user of the machine be required to move the movable mass that is indicated on the machine throughout the entire range of motion of the mass, in order to provide a relatively accurate measure of the user's level of work/effort. The present invention recognizes that a weight machine can be provided that is adjustable to suit the requirements of different users and that requires a substantially constant force to move the mass through its entire range of motion.
Accordingly, it is an object of the present invention to provide an exercise device that is adjustable to suit more than one user. Another object of the present invention is to provide an exercise device that requires a substantially constant force to move the device through its range of motion. Further, it is an object of the present invention to provide an exercise device that has moving parts capable of being smoothly moved through their entire range of motion. Finally, it is an object of the present invention to provide an exercise device that is easy to use and cost-effective to manufacture.